The present invention relates to an improved diode, known as a "Femto Diode", for use in the light-electric power converter (LEPCON.TM.), and many other applications: high-power laser D.C. electric-light conversion, super high speed light-electric communication and computer operation. The Femto Diode is capable of rectifying electric oscillations having Femto (10.sup.-15) second periods corresponding to the visible light range; that is, operating in the frequency range of 4 to 8.times.10.sup.14 Hz, which is greater than heretofore possible with prior art devices. The Femto Diode of this invention has the new, unusual, and long-sought property of operation in the light frequency range. Table 1 shows light color versus wavelength, period, frequency and energy in practical and MKS/SI Units.
The Femto Diode of this invention utilizes an assymetric tunnel junction comprising a metal 1/insulator/metal 2 in a wall step configuration. New and novel combinations of materials and dimensions are disclosed to maximize the forward/reverse current ratio. The materials are simple, inexpensive, readily available and nontoxic.
New metals and combinations with oxides are utilized in the tunnel junction to obtain the particular values of the work functions .phi..sub.1 and .phi..sub.2 of metals 1 and 2, barrier thickness s and cross-sectional area A for optimum electrical properties. The diode structure may be protected by vacuum, inert gas, encapsulating glass or plastic layers, or laminated to prevent a destructive reaction with air (oxygen) and/or water.
A comprehensive review and bibliography on Electron Tunnelling through an insulating barrier has been given.sup.1. Tunnel Diodes (metal/oxide/metal) were observed to rectify at optical frequencies but the response was small..sup.2,3,4
These prior art junctions were symmetric in structures: Al/Al.sub.2 O.sub.3 /Al or Ni/NiO/Ni with a minimum cross-sectional area 1000 .ANG..times.1000 .ANG.; the antenna used was in the micron length range and so performed poorly in the quantum regime. The need for a new approach was stressed..sup.3.1
The mathematical physics theory of Symmetric Tunnel Junctions has been described.sup.5,6,7 ; and extended to an Assymmetric Tunnel Junction, on which the basic equations were established..sup.8 However, the particular conditions requisite for a tunnel junction suitable for use in the quantum regime were unknown; in particular the conditions required for a high tunnel probability suitable for use in the Femto Diode of this invention were not known.
TABLE I __________________________________________________________________________ LIGHT-COLOR VS. WAVELENGTH, PERIOD, ANGULAR FREQUENCY, FREQUENCY AND ENERGY ANGULAR NAME COLOR WAVELENGTH PERIOD FREQUENCY FREQUENCY ENERGY __________________________________________________________________________ SYMBOL -- .lambda. T .omega. .nu. .epsilon. UNITS -- .ANG. BEMTOSEC RADIANS HERTZ eV = h.nu. -- PRACTICAL ANGSTROMS PER SEC CYCLES/SEC ELECTRON- VOLTS UNITS -- 10.sup.-10 m 10.sup.-15 S .times. 10.sup.-15 .times. 10.sup.15 -- JOULES MKS/IU .times. 10.sup.-19 -- RED 7000 2.336 2.69 0.428 1.77 2.835 -- GREEN 5600 1.869 3.36 0.535 2.21 3.540 -- BLUE 4000 1.333 4.71 0.750 3.1 4.966 __________________________________________________________________________